Apparatus and method of measuring features in stacked dies

Abstract

A method includes bonding a second die including second feature to a first die. The first die includes a first feature. A first image of at least a portion of the first die is captured using a first image sensor disposed at a first angle that is normal to the first surface. A second image of at least a portion of the second die is captured using a second image sensor disposed at a second angle. The first and second images include at least a portion of the first feature and the second feature. At least one offset between the features are determined based on the first image and the second image. An alignment correction between the dies are determined based on the offset. One or more alignment commands are sent based on the alignment correction to a robot end effector system of an optical inspection system.

What is claimed is: 
     
         1 . A method for forming a device, the method comprising:
 bonding a second die, which has a second feature formed on a first surface of the second die, to a first die, wherein the first die having a first feature formed on a first surface of the first die;   capturing a first image of at least a portion of the first die using a first image sensor disposed at a first angle from a first direction that is normal to the first surface of the first die;   capturing a second image of at least a portion of the second die using a second image sensor disposed at a second angle from the first direction, the first image and the second image including at least a portion of the first feature and at least a portion of the second feature;   determining at least one offset between the first feature and the second feature based on the first image and the second image;   determining an alignment correction between the first die and the second die based on the at least one offset; and   sending one or more alignment commands based on the determined alignment correction to a robot end effector system of an optical inspection system.   
     
     
         2 . The method of  claim 1 , wherein the first angle and the second angle are oriented in opposite directions relative to the first direction and equal in magnitude. 
     
     
         3 . The method of  claim 1 , wherein the first image sensor and the second image sensor are in communication with a controller of an optical inspection system. 
     
     
         4 . The method of  claim 1 , further comprising generating a 3D reconstruction based on a comparison of pixels in the first image and the second image. 
     
     
         5 . The method of  claim 4 , further comprising:
 determining orientation information between the first die and the second die based on the 3D reconstruction and storing the orientation information, wherein the orientation information indicates an orientation and position between the first die and the second die.   
     
     
         6 . The method of  claim 1 , wherein a cross-sectional shape of the first feature is a circle having a first critical dimension, a cross-sectional shape of the second feature is a circle having a second critical dimension, and the first critical dimension and the second critical dimension are equal. 
     
     
         7 . The method of  claim 1 , wherein determining an alignment correction between the first die and the second die based on the at least one offset comprises determining an alignment correction that causes the second feature to be in alignment with the first feature in a subsequent device. 
     
     
         8 . An optical inspection system comprising:
 an imaging device, the imaging device comprising:
 a first image sensor disposed at a first angle from a first direction that is normal to a first surface of a first die of a stacked semiconductor assembly; 
 a second image sensor disposed at a second angle from the first direction; 
 a controller coupled to the first image sensor and the second image sensor; and 
 a memory for storing a program to be executed in the controller, the program comprising instructions when executed cause the controller to: 
 capture a first image of the device using the first image sensor, the device comprising a second die bonded to a first die that is bonded to a base substrate, the first die having a first feature formed on a first surface of the first die and the second die having a second feature formed on a first surface of the second die; 
 capture a second image of the device using the second image sensor, the first image and the second image including at least a portion of the first feature and at least a portion of the second feature; 
 determine at least one offset between the first feature and the second feature based on the first image and the second image; 
 determine an alignment correction between the first die and the second die based on the at least one offset; and 
 send one or more alignment commands based on the alignment correction to a robot end effector system of the optical inspection system for use in forming a subsequent device. 
   
     
     
         9 . The optical inspection system of  claim 8 , wherein the first angle and the second angle are oriented in opposite directions relative to the first direction and are equal in magnitude. 
     
     
         10 . The optical inspection system of  claim 8 , wherein the instructions further comprise instructions to generate a 3D reconstruction based on a comparison of pixels in the first image and the second image. 
     
     
         11 . The optical inspection system of  claim 10 , wherein the instructions further comprise instructions to determine orientation information between the first die and the second die based on the 3D reconstruction and store the orientation information in the memory, wherein the orientation information indicates an orientation and position between the first die and the second die. 
     
     
         12 . The optical inspection system of  claim 8 , wherein a cross-sectional shape of the first feature is a circle having a first critical dimension, a cross-sectional shape of the second feature is a circle having a second critical dimension, and the first critical dimension and the second critical dimension are equal. 
     
     
         13 . The optical inspection system of  claim 8 , wherein the instructions for determining an alignment correction between the first die and the second die based on the at least one offset further comprise instructions to determine an alignment correction that causes the second feature to be in alignment with the first feature in a subsequent device. 
     
     
         14 . The optical inspection system of  claim 8 , wherein the alignment correction is determined based on a pre-determined distance between a center of the first feature and a center of the second feature. 
     
     
         15 . An imaging device comprising:
 a first image sensor disposed at a first angle from a first direction that is normal to a first surface of a first die of a stacked semiconductor assembly;   a second image sensor disposed at a second angle from the first direction;   a controller coupled to the first image sensor and the second image sensor; and   a memory for storing a program to be executed in the controller, the program comprising instructions when executed cause the controller to:   capture a first image of the device using the first image sensor, the device comprising a second die bonded to a first die that is bonded to a base substrate, the first die having a first feature formed on a first surface of the first die and the second die having a second feature formed on a first surface of the second die;   capture a second image of the device using the second image sensor, the first image and the second image including at least a portion of the first feature and at least a portion of the second feature;   determine at least one offset between the first feature and the second feature based on the first image and the second image;   determine an alignment correction between the first die and the second die based on the at least one offset; and   send updated alignment commands based on the alignment correction to a robot end effector system of an optical inspection system for use in forming a subsequent device.   
     
     
         16 . The imaging device of  claim 15 , wherein the first angle and the second angle are oriented in opposite directions and equal in magnitude. 
     
     
         17 . The imaging device of  claim 15 , wherein the instructions further comprise instructions to generate a 3D reconstruction based on a comparison of pixels in the first image and the second image. 
     
     
         18 . The imaging device of  claim 17 , wherein the instructions to determine at least one offset between the first feature and the second feature in at least one direction perpendicular to the first direction comprise instructions to determine a difference between at least one of a distance between a center of the first feature and a center of the second feature and a predetermined distance in the first image and a distance between the center of the first feature and the center of the second feature and a predetermined distance in the second image. 
     
     
         19 . The imaging device of  claim 15 , wherein a cross-sectional shape of the first feature is a circle having a first critical dimension, a cross-sectional shape of the second feature is a circle having a second critical dimension, and the first critical dimension and the second critical dimension are equal. 
     
     
         20 . The imaging device of  claim 15 , wherein the alignment correction is determined based on a pre-determined distance between a center of the first feature and a center of the second feature.